The disclosure is directed toward applications for very short reach optical interconnects, such as intrachip or chip-to-chip communications, where power consumption, reliability and yield requirements cannot be met by existing semiconductor laser technologies.
The number and density of integrated circuit devices that require interconnection at the intrachip level continues to grow at a furious pace in accordance with Gordon Moore's famous prediction (i.e., the number of transistors per square inch on integrated circuits has doubled every 18 months since the integrated circuit was invented). Research into the projected saturation of integrated circuit technology, due to the physical limitations and scaling behavior of electrical wires, has highlighted the need to investigate unconventional solutions, such as optical interconnects, to allow continued progress.
Analysis suggests that such optical interconnects can provide configurable and scalable solutions for intrachip and chip-to-chip global communications while significantly improving bandwidth, delay, noise, and real-estate consumption for next generation VLSI systems. However, several expert authors have claimed that optical interconnects are not practical for very short reach applications. This claim is primarily due to the unavailability of low cost, high-density, high-yield and reliable optical sources. Existing semiconductor laser technologies are targeted for long haul/reach communications applications and provide high optical power. In contrast, short reach applications, such as between points on a chip in multi-chip modules (MCM), where the maximum path length is on the order of centimeters, do not require such high optical power, but need high-reliability, high density of sources and sinks, low heat dissipation and low cost.
Background art discloses that high-density arrays of modulators, such as Multiple Quantum Well Modulators (MQWMs), have been fabricated that provide high-yield, low-power operation and extended mean-time-to-failure (MTTF). However, using modulators efficiently in an optical architecture requires a method and apparatus for coupling to and from the modulated effective source.
Further, background art modulator-based optical interconnect methods use spot array generators and a beam splitter to couple light to modulators. However, with these background art methods, the space above the plane of the modulators is at least partially obstructed, making integration with interconnect fabrics difficult. In addition, the regular pattern of a spot array generator does not allow arbitrary placement of the source points.
Therefore, there is a need in the art for methods and apparatus coupling an external optical source to modulators to create high density and low electrical power consumption optical sources and sinks that can be efficiently coupled to optical interconnect systems.